It is known to blend two or more polymeric materials to achieve beneficial performance characteristics in the resulting polymeric composition. One such conventional blending process is the blending of elastomeric and thermoplastic polymeric materials. For example, as described in U.S. Pat. No. 6,642,316, it is known to blend ethylene propylene based interpolymers with polypropylene so as to provide a polypropylene dispersed phase and an elastomeric continuous matrix phase. The overall blend may be elastomeric in nature. The ethylene propylene based interpolymers may be of the type described in WO 02/083754. WO 04/060994 discloses the production of elastomeric blends by blending propylene rich polymers with minor amounts of ethylene polymers to produce blends having a continuous phase of the propylene rich polymer and a dispersed phase of the ethylene polymer.
High density polyethylene polymers are widely used in a variety of molded and extruded articles such as containers and pipes. Pipes made using high density polyethylene are lightweight and can be easily assembled by fusion welding. Polyethylene pipes also have good flexibility and are corrosion free. PCT Published Applications WO/91/19763; WO 02/0903393; and WO 2004/031291 disclose polyethylene polymers and polymer blends with improved environmental stress crack resistance properties.
Other background references include WO 2000/70134.